Energy analysis method for hidden damage detection

Abstract

A method of detecting internal defects in composites or other multilayer materials includes generating a wavefield on a surface of the material. Wavefield data is collected from the wavefield on the surface, and the measured wavefield data is processed to provide measured energy data. The method may include generating simulated or predicted energy data for the multilayer material that is compared to the simulated energy data to determine if the multilayer material has internal defects or damage below the surface. The method can be utilized to detect and/or quantify damage or other defects that are “hidden” by damage that is closer to the surface of the material.

The invention claimed is: 
     
       1. A method of detecting hidden internal defects in a component comprising a multi layer material from a single side of a surface of the component, the method comprising:
 connecting at least one transducer to the component; 
 actuating the transducer to generate an ultrasonic guided wavefield in the multilayer material and on the surface of the multilayer material such that guided wave energy is trapped near the surface due to a first defect below the surface; 
 collecting wavefield data from the ultrasonic guided wavefield on the surface of the multi layer material at the single side, without contacting the multilayer material, using a non-contact laser Doppler vibrometer or an air-coupled ultrasound device; 
 processing the wavefield data, including calculating a cumulative amount of the guided wave energy trapped near the surface using the collected wavefield data; and 
 identifying and/or quantifying whether the multilayer material has hidden internal defects that are further from the surface than the first defect and overlap the first defect, including comparing the calculated cumulative guided wave energy to the known cumulative energy data for a sample set of the multilayer materials having known hidden internal defects. 
 
     
     
       2. The method of  claim 1 , wherein:
 the component comprises a multilayer composite material having a matrix material and a plurality of layers of fibers. 
 
     
     
       3. The method of  claim 2 , wherein:
 the matrix comprises a polymer material, and the layers of fibers comprise carbon fibers. 
 
     
     
       4. The method of  claim 3 , wherein connecting at least one transducer to a component includes imbedding a plurality of piezoelectric transducers in the multi layer composite material prior to curing the multi layer composite material, and wherein actuating the transducer includes actuating the plurality of piezoelectric transducers after curing the multilayer composite material. 
     
     
       5. The method of  claim 1 , wherein:
 the hidden internal defects comprise damage in the form of at least one hidden delamination. 
 
     
     
       6. The method of  claim 5 , wherein:
 the damage comprises a first delamination and a second delamination that is spaced apart from the first delamination and at least partially overlaps the first delamination, and wherein the second delamination is directly between the surface of the component and the first delamination. 
 
     
     
       7. The method of  claim 6 , wherein:
 the damage further comprises a third delamination, and wherein the first and second delaminations are spared apart from the third delamination, and wherein the first and second delaminations are between the third delamination and the surface of the item and wherein the third delamination at least partially overlaps the first and second delaminations. 
 
     
     
       8. The method of  claim 1 , wherein:
 the component comprises an aircraft structure. 
 
     
     
       9. The method of  claim 1 , wherein:
 the known cumulative guided wave energy data comprises simulated cumulative guided wave energy data. 
 
     
     
       10. The method of  claim 1 , wherein:
 the known cumulative guided wave energy data comprises empirical energy data collected from multilayer material samples having hidden internal damage. 
 
     
     
       11. The method of  claim 1 , wherein collecting wavefield data from the ultrasonic guided wavefield includes using a plurality of laser beams to scan the surface from the single side. 
     
     
       12. A method of detecting internal defects in a multilayer material having a surface from a single side of the surface, the method comprising:
 applying a force to the multilayer material using a piezoelectric transducer such that an ultrasonic guided wave is excited in the multilayer material and on the surface of the multilayer material, and such that guided wave energy is trapped near the surface due to at least one hidden internal defect below the surface; 
 measuring, from the single side using a laser Doppler vibrometer or an air-coupled ultrasound device that does not contact the multilayer material, a response of the surface to the applied force to provide measured surface response data, including calculating a cumulative amount of the guided wave energy trapped near the surface using the collected wavefield data; 
 comparing the measured surface response data to known data that correlates surface responses for the multilayer material to internal defects in the material, the known data corresponding to at least one outer internal defect and the at least one hidden internal defect that is disposed a greater distance from the surface than the outer internal defect, and wherein the outer internal defect and the at least one hidden internal defect at least partially overlie one another; and 
 determining if the at least one hidden internal defect is present and/or quantifying at least one hidden internal defect by comparing the measured surface response data to the known data. 
 
     
     
       13. The method of  claim 12 , wherein:
 the known data comprises surface response data for internal damage. 
 
     
     
       14. The method of  claim 13 , wherein:
 the known data comprises simulated surface response data. 
 
     
     
       15. The method of  claim 13 , wherein:
 the known data comprises empirical data for the multilayer material that is generated by measuring the surface response of samples having internal damage including at least one hidden internal defect. 
 
     
     
       16. The method  claim 12 , wherein applying the force to the multilayer material includes:
 exciting the piezoelectric transducer using a windowed sine wave. 
 
     
     
       17. The method of  claim 12 , wherein:
 measuring the response of the surface further includes measuring at least one of a displacement and a velocity of the surface. 
 
     
     
       18. The method of  claim 12 , wherein:
 the known data comprises simulated cumulative guided wave energy data; and 
 comparing the measured cumulative guided wave energy data to the simulated cumulative energy data to determine if the hidden internal defect is present and/or to quantify the hidden internal defect. 
 
     
     
       19. The method of  claim 12 , wherein:
 the force is applied to the surface in a direction that is transverse to the surface.